Submitted to: Pedobiologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 14, 2003
Publication Date: December 20, 2003
Citation: SHUSTER, W.D., SHIPITALO, M.J., BOHLEN, P.J., SUBLER, S., EDWARDS, C.A. POPULATION DYNAMICS OF AMBIENT AND ALTERED EARTHWORM COMMUNITIES IN ROW-CROP AGROECOSYSTEMS IN THE MIDWESTERN U.S. PEDOBIOLOGIA. 2003. v. 47 p. 825-829.
Interpretive Summary: Earthworms are often the dominant soil organism in many agricultural fields. By burrowing in the soil and ingesting crop residues they affect the structure of the soil and the availability of plant nutrients. Thus, earthworms can alter plant growth and nutrient cycling. Tillage operations, however, can lead to a reduction in earthworm populations. Deep burrowing earthworm species are particularly affected by tillage because it buries the crop residue they reply on for food. In this study we added deep burrowing earthworms to chisel-tilled plots and to less intensively tilled plots in a ridge-till crop rotation. We found the added earthworms persisted only in the ridge-tilled plots and that the additions only temporarily reduced the populations of shallow burrowing earthworms. This research will benefit farmers in that they should be able to increase earthworms populations by reducing tillage and increasing the amount of crop residue left on the soil surface.
Although earthworms affect agroecosystem processes, few studies have addressed population dynamics when earthworms are intentionally introduced. Therefore, handsorting and formalin extraction were used semi-annually from fall 1994 to fall 1997 to measure populations in ambient and addition plots in chisel (CS, Corn-Soybean) and ridge-tilled (CSW, Corn-Soybean-Wheat) rotations in Ohio, USA. Earthworm communities were altered by adding 76 Lumbricus terrestris (L.)per square meter each spring and fall into plots with no, or very few of these anecic earthworms. Increases in L. terrestris were small (7 per square meter) compared to the number added and their establishment was at the expense of the epigeic earthworm L. rubellus (Hoff.), which declined four and two-fold in CS and CSW systems, respectively. Populations of the endogeic earthworm Octolasion tytaeum (Sav.) were unaffected by the additions. Sampling 5 years after the additions indicated that L. terrestris persisted only in the CSW plots. The decline in L. rubellus populations in plots with added anecic worms was no longer evident. Thus, earthworm populations in these agroecosystems were related to disturbance regimes and resource distribution, and were affected by competitive interactions between different functional groups.